From 7d9dfc27ee2196394d97b0c45e84eb948e9f1de2 Mon Sep 17 00:00:00 2001
From: Jensun Ravichandran <jjensun@gmail.com>
Date: Thu, 22 Apr 2021 13:12:19 +0200
Subject: [PATCH] Add similarities file

---
 prototorch/functions/similarities.py | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 prototorch/functions/similarities.py

diff --git a/prototorch/functions/similarities.py b/prototorch/functions/similarities.py
new file mode 100644
index 0000000..cc91c78
--- /dev/null
+++ b/prototorch/functions/similarities.py
@@ -0,0 +1,18 @@
+"""ProtoTorch similarity functions."""
+
+import torch
+
+
+def cosine_similarity(x, y):
+    """Compute the cosine similarity between :math:`x` and :math:`y`.
+
+    Expected dimension of x is 2.
+    Expected dimension of y is 2.
+    """
+    norm_x = x.pow(2).sum(1).sqrt()
+    norm_y = y.pow(2).sum(1).sqrt()
+    norm_mat = norm_x.unsqueeze(-1) @ norm_y.unsqueeze(-1).T
+    epsilon = torch.finfo(norm_mat.dtype).eps
+    norm_mat.clamp_(min=epsilon)
+    similarities = (x @ y.T) / norm_mat
+    return similarities